Abstract: As an important method monitoring fish passage efficiency with high reliability, precision, and automation, passive integrated transponder (PIT) telemetry has been widely used. During field monitoring, a crucial issue for ensuring data accuracy is how to maintain high-precision monitoring under interference from external environment. Based on video data on fish passing the PIT antenna, we tested the monitoring effectiveness of the halfduplex (HDX) PIT telemetry system, and analyzed the effects of the number and movement direction of fish on the accuracy of the HDX PIT telemetry system. The results showed that the monitoring effectiveness of the HDX PIT telemetry system was satisfactory. The mean error time of the tested fish through antenna with two sizes (Ⅱ, big size; Ⅰ, small size) was (0.40±0.46) s (Mean±SD), with the maximum error being 2.53 s. The number of crossing fish significantly affected the detection efficiency of antenna with two sizes. When a fish passed through the antenna, the detection efficiency of antenna Ⅱ and Ⅰ was 97.3% and 93.9%, respectively. When the number of fish increased to eight, the detection efficiency of antenna Ⅱ and Ⅰ decreased to 7.5% and 3.1%, respectively. The direction of crossing fish affected the detection efficiency of antenna Ⅰ, but not on that of antenna Ⅱ. We provide feasible suggestions to promote reliability of monitoring data for PIT telemetry system.

Key words: abrupt change, climate change, variation of runoff and sediment flux, main cycle, human activity, Mun River Basin, fish passage, fish passage efficiency, PIT telemetry, detection efficiency.